fixed issue that package manager was not being able to load lightweight pipeline resources properly.

ScriptableRenderPipeline/LightweightPipeline/Resources/LightweightPipelineAsset.cs

     {
         public static readonly string m_SimpleLightShaderPath = "LightweightPipeline/Standard (Simple Lighting)";
         public static readonly string m_StandardShaderPath = "LightweightPipeline/Standard (Physically Based)";
+        public static readonly string[] m_SearchPaths = {"Assets", "Packages/com.unity.render-pipelines"};
 
         // Default values set when a new LightweightPipeline asset is created
         [SerializeField] private int m_MaxPixelLights = 4;
         {
             var instance = CreateInstance<LightweightPipelineAsset>();
 
-            string[] guids = UnityEditor.AssetDatabase.FindAssets("LightweightPipelineResource t:scriptableobject");
+            string[] guids = UnityEditor.AssetDatabase.FindAssets("LightweightPipelineResource t:scriptableobject", m_SearchPaths);
             LightweightPipelineResource resourceAsset = null;
             foreach (string guid in guids)
             {
                     break;
+            }
+
+            // There's currently an issue that prevents FindAssets from find resources withing the package folder.
+            if (resourceAsset == null)
+            {
+                string path = "Packages/com.unity.render-pipelines.lightweight/Resources/LightweightPipelineResource.asset";
+                resourceAsset = UnityEditor.AssetDatabase.LoadAssetAtPath<LightweightPipelineResource>(path);
             }
 
             if (resourceAsset != null)

ScriptableRenderPipeline/LightweightPipeline/Resources/LightweightPipelineResource.asset

   m_Script: {fileID: 11500000, guid: eb91b173ce266e040aa972ca9a561308, type: 3}
   m_Name: LightweightPipelineResource
   m_EditorClassIdentifier: 
-  DefaultMaterial: {fileID: 0}
-  DefaultParticleMaterial: {fileID: 0}
-  DefaultTerrainMaterial: {fileID: 0}
+  DefaultMaterial: {fileID: 2100000, guid: 31321ba15b8f8eb4c954353edc038b1d, type: 2}
+  DefaultParticleMaterial: {fileID: 2100000, guid: e823cd5b5d27c0f4b8256e7c12ee3e6d,
+    type: 2}
+  DefaultTerrainMaterial: {fileID: 2100000, guid: 594ea882c5a793440b60ff72d896021e,
+    type: 2}